000 AXPZ20 KNHC 151606 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Tue May 15 2018 Tropical Weather Discussion for the eastern Pacific Ocean from the Equator to 32N, east of 140W. The following information is based on satellite imagery, weather observations, radar, and meteorological analysis. Based on 1200 UTC surface analysis and satellite imagery through 1415 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 07N77W TO 08.5N89W TO 06.5N105W TO LOW PRES NEAR 11.5N116W 1008 MB TO 05N123W, where latest scatterometer data indicated that it transitions to the ITCZ to 01.5N135W. Scattered moderate to strong convection is located within 180 nm S and 210 nm N of the trough between 86W and 122W. Scattered moderate isolated strong convection is within 90 nm of the Central American coast between 85W and 93W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A NW to SE oriented high pressure ridge prevails across the offshore waters west of Baja California, producing fresh NW winds over those waters. These winds will remain fresh today, then increase to fresh to locally strong Wed afternoon through Friday as the ridge strengthens slightly. Altimeter data from last night indicated that seas were just below 8 ft, in the 5-7 ft range. Seas will change little through tonight before building slightly on Wed to 6-8 ft. Gulf of California: S to SW winds of around 15 kt over a small section of the northern Gulf of California will become light and variable today. Gentle to moderate NW winds will continue across the remainder of the Gulf through Wed, except for fresh NW winds along the coast of Mexico from 24N to 26N beginning late this afternoon through Wed evening. Gulf of Tehuantepec: S to SW winds are light to gentle across the Gulf this morning. Winds will briefly become moderate fresh N to NE tonight into Wed morning, then become gentle S to SW winds on Wed afternoon. This cycle of changing winds will repeat through Thu as a weak pressure pattern remains over Mexico. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Light to gentle winds will dominate the gulf most of the forecast period as a weak pressure remains across Central America. Seas of 5-6 ft prevail this morning and will diminish slightly today to 4-5 ft in long period SW swell. A strong pulse of cross equatorial SW swell will move into the regional waters beginning Wed, and build seas to 5-7 ft Thu through Sat. Gulf of Panama: Gentle to moderate S to SW winds are forecast during the next several days, with seas of 4-6 ft in long period southerly swell, building to 5-7 ft Wed night through Sat as long period SW swell reaches the coasts of Panama and Colombia. Elsewhere, gentle to moderate SW winds are expected to the south of the monsoon trough with its axis roughly along 09N/10N, with light to gentle variable winds north of trough as a weak pressure pattern remains over Central America. Seas are forecast to build to 6-7 ft in long period SW swell between Ecuador and the Galapagos Islands beginning on Wed and continuing through Fri, then build slightly higher to 6-8 ft Sat. REMAINDER OF THE AREA... A ridge extends from the NW waters southeastward to near the Revillagigedo Islands. The pressure gradient between the ridge and the monsoon trough and ITCZ to the south is presently weak, and yielding moderate NE-E trades between about 10N and 22N to the west of 112W. Seas across this area of trades are 6-8 ft, and should change little through Thu. The ridge will shift slightly southeastward through Wed, with the resultant pressure gradient forecast to induce a slight increase of trades across the tropics. Stronger high pressure is then forecast to build southeastward over the northern portion of the discussion area, with and even tighter gradient expected to lead to trades increasing to fresh to strong speeds. Seas are expected to increase to 7-9 ft Thu into Fri. The low 1008 mb low pressure embedded within the monsoon trough as described above continues to shift westward at 10-15 kt across the tropics this morning. Global models depict the low continuing to move in a general west to southwest motion through Fri while it weakens. Fresh to strong winds will remain across the NW quadrant of the low as it shifts westward, where seas of 7-8 ft will accompany it. Decaying NW swell is propagating through the waters north of 21N between Baja California and 117W, where seas peaked at 7-8 ft overnight. These seas will subside to 5-7 late tonight and change little through Thu. $$ Stripling